The development of steam cracking units which can be expected in the future will introduce into the market an excess of normal butanes and isobutanes and it will be therefore necessary to find new uses for these materials. As a matter of fact, the increasing demand of ethylene, propylene and benzene will also result in an excess of olefinic C.sub.4 cut as obtained from butadiene extraction plants.
It has already been proposed in the French Pat. No. 1,417,238 (or the Canadian Pat. No. 803,572) to convert C.sub.4 cuts to gasoline by a process wherein the C.sub.4 cut is subjected to polymerization followed with hydrogenation of the resultant polymers. However this process is not selective since, particularly in the course of the polymerization, there are obtained mixtures of isobutene dimers and trimers, pentenes, hexenes and heptenes and, consequently various hydrocarbon mixtures during the hydrogenation step which follows the polymerization.